How to run the print test
Several real sizes, then a phone, then a note of what failed.
test sheet draws the same symbol at 15, 20, 25, 30, and 40 mm. Print it. Scan each size from the distance you care about, in the light you care about. Write down the smallest size that worked. That note is more useful than the on-screen ratio.
The page says, and means, that a visual pass does not guarantee a scan. Damaged corners, heavy varnish, and dark brand colors are outside the math.
Use error correction M, which is what the generator uses. If the artwork will be creased, test a higher correction in another tool before you rely on this sheet. This version does not switch correction levels.